Our family recently unveiled the headstone on my mother's grave. Before the unveiling service, my elder brother told me NOT to walk over the grave of my mother. Through lack of space it was impossible to assemble the relatives together so as NOT to stand on the grass over her grave. Is there a law or custom not to walk on the graves of the dead? If so, why are gravestones not placed horizontally on top of the earth, rather than vertically at the head of the grave? Is the custom different in Israel?
Nit'e Gavriel, Mourning volume 2, chapter 87, paragraphs 11–12 (page 669):
And chapter 66, paragraph 25:
See his footnotes for citations and reasons.
Oh, and chapter 66 (about gravestones), paragraph 19: